How will the friction force acting on the bar change, if the mass of the bar is changed, it is reduced by 3 times?

Given:

m2 = m1 / 3 – the mass of the bar was reduced by 3 times;

k1 = k2 = k is the coefficient of friction of the bar against the surface;

g is the acceleration of gravity.

It is required to determine F2 / F1 – how will the friction force acting on the bar change with a decrease in the bar mass.

Since it is not specified in the problem statement, it considers that the bar is on a flat surface.

Then, the friction force in the first case will be equal to:

F1 = k1 * N1 = k * m1 * g.

The friction force in the second case will be equal to:

F2 = k2 * N2 = k * m2 * g = k * m1 * g / 3.

F2 / F1 = (k * m1 * g) / (k * m1 * g / 3) = 3 times.

Answer: with a decrease in the mass of the bar, the friction force will decrease by 2 times.